(1) Field of the Invention
The present invention relates to a video editing system for editing videos, and to a method thereof.
(2) Description of the Related Art
In a known editing system, editing is performed, for example, in such a way that desired shots are selected from an original source, that is, one roll of video tape including pictures taken by a video camera etc., and dubbed in a master tape.
In such a case, a transitional technique such as wipes or dissolves is applied to a joint between one shot and another on the master tape to further improve a vide effect. The transitional techniques is a technique to gradually replace one shot with a following one continuing in time. With "Wipes", a preceding SHOT A is partly broken away and a following SHOT B is projected in the broken-away part, so that the SHOT A is gradually replaced with the SHOT B as the former fades out while the latter fades in. Whereas with "Dissolves", the picture elements of the preceding SHOT A and those of the following SHOT B in the same locations are composed at a specified rate, and the former is gradually replaced with the latter as the rate changes.
To effect the time-series transition on videos with wipes or dissolves, a technique is required such that combines the SHOT A and the SHOT B by reproducing them in respective channels or reading them out from respective storage units while they are being recorded on a master tape.
On the other hand, the need for effecting the transitional technique to a combined video, or so-called "Picture-in-picture", has been increasing in recent years. This means the video editing system must combine three or more shots simultaneously. Although, systems can be constructed for combining three or more shots simultaneously on real time, it complicates the hardware thereof and costs too much for practical use. Also, such systems combine only a fixed number of shots, making it impossible to operate flexibly where three shots are to be combined in one case, and four shots or five shots in other cases.
To avoid this problem, several techniques have been proposed for combining three or more shots by using an inexpensive conventional video effect unit which is originally designed to combine only two shots simultaneously.
In one of such techniques, 2-shot-combining is repeated. More precisely, assuming that three shots are combined simultaneously, two shots are initially combined by the video effect unit and recorded in a tape which is used as a new original source; another shot is combined with the firstly combined shot on the tape while it is reproduced; and the secondly combined shot is recorded on a master tape.
According to this technique, three shots can be combined by using the video effect unit twice, and four shots for three times. However, each combined shot must be recorded on a tape, and the tape must be reproduced as a new original source for a following 2-shot-combining. Thus, this technique also poses a problem that the entire process is laborious and undesirably takes a long time.
In another one of such techniques, a plurality of the video effect units are connected to each other. More precisely, a first video effect unit 101 is connected to a second video effect unit 102 as is shown in FIG. 1; two shots are read out simultaneously from respective video storage units 103, 104, and combined at the first video editing unit 101; the firstly combined shot is again combined with another shot read out from another video storage unit 105 at the second video editing unit 102; and the secondly combined shot is displayed at a display unit 106.
However, according to this technique, the number of the video effect units increases as the number of shots increases, and so does the cost of production.